Some DVD sets of public domain episodes have the classic theme song replaced by generic music due to copyright disputes.
During their original airings, episodes ran exactly 24 1/2 minutes (not counting commercial time). Most syndication prints now run 22 minutes to allow for additional commercial time. Some of the missing material (which includes the episode epilogues and other miscellaneous scenes) has been restored to VHS and DVD releases of various "Andy Griffith" episodes.
During the CBS network run, the closing credits showed Andy and Opie walking back from their fishing trip. Opie drops the fish, and runs back to get them. One of the original sponsor's products (Sanka coffee, for instance) would appear in the corner of the screen. The syndicated reruns show a plain gray background (or blue, during the color years) with a drawing of the town square in the corner of the screen that once displayed the sponsor's product.